Megaman Zero 1 - The beginning of all, has some solid gameplay, but a quirky level design.

Megaman Zero 2 - Has some improvements on it, doing s ranks is much more enjoyable.

Megaman Zero 3 - The peak of this style of Megaman, has a really fun combo system and good level design. For me it's the peak of the story of this franchise, since Omega exists, he has many weight and symbolic meaning to it's character.

Megaman Zero 4 - Literally the end, Zero fucking died LMAO